Gasification systems are in general well known for the conversion of biomass material into carbon and/or ash, with the production of synthetic fuel gas (syn gas) being the major product of the system. Examples of such a gasification system generally similar to that of the present invention are shown in U.S. Pat. No. 4,530,702 to Fetters et al, and more recently, in U.S. Pat. No. 5,106,390 to Beierle et al. While such gasifiers have been known to perform well under certain controlled conditions, it has been difficult to obtain consistent, reliable results from such gasifiers over extended, continuous operating times, i.e. 24 hours to several days, times which are necessary for practical commercial operation. There are often difficulties with the actual physical structure of the gasifier, particularly the welds and rivets thereof. Such difficulties are principally caused by the very high internal temperatures of the gasifier, produced by the pyrolysis reaction in the gas production bed established in the gasifier, in combination with the frequent start-ups and shut-downs encountered in normal operation and the resulting expansion/contraction stress produced on the metal components of the gasifier.
In addition, there are often difficulties with maintaining the uniformity of the pyrolysis zone and in insuring the absence of channeling in the gas production bed. Further, there is often turbulence which exists at the gas discharge ports, caused by the movement of gas as it proceeds from the gas production bed through the discharge ports. During operation, it is important to maintain the lower section of the gas production bed in a highly controlled state, including strict control over the introduction of oxygen into the gas production bed as well as over the respective temperatures and depth of the various portions of the production bed.
It is also important to prevent the introduction of air into the gasification system from the rear end of the system, i.e. at the point where the carbon or ash residue is removed from the system, and thereby also insure continued operation of the gasifier during carbon off-loading.
Further, it is important to distribute the fuel properly upon its entry into the upper portion of the gasifier. This helps to insure proper operation of the gasifier.